1) Find 3 lawyers and get a quotation in the man time - usually directly after booking. SPA & LA prepared by your appointed lawyer.
2) If got sufficient Life / Medical and no affect interest rate - no need to buy
3) Yes, but can do prior to booking
4) Check value before putting in a booking - your agent can assist.

Always pay to the registered agency - not to any individual's bank account that claims to act on behalf of any agency.

Also when paying the booking fee, always stress in the clause that your loan should be fully refunded if loan is rejected AND if loan is approved below 90% (means even if your loan is approved at 89.9%, you have the rights to get back your booking fee).